Slashdot Mirror
BBC Lowers HDTV Bitrate; Users Notice
aws910 writes "According to an article on the BBC website, BBC HD lowered the bitrate of their broadcasts by almost 50% and are surprised that users noticed. From the article: 'The replacement encoders work at a bitrate of 9.7Mbps (megabits per second), while their predecessors worked at 16Mbps, the standard for other broadcasters.' The BBC claims 'We did extensive testing on the new encoders which showed that they could produce pictures at the same or even better quality than the old encoders ...' I got a good laugh off of this, but is it really possible to get better quality from a lower bitrate?"
...of blind retards.
THL phish sticks
They also lowered their math standards. From 16MBps to 9.7 MBps is a 40% reduction, not "almost 50%".
I've abandoned my search for truth; now I'm just looking for some useful delusions.
Yes, if more time and passes are spent encoding the video, lower bitrate CAN result in a higher quality video. However, this does not appear to be the case in this instance.
Sure, if you also switch to a better codec, such as using H.264 instead of MPEG-2. However, I don't think that's what's happening in this case.
but is it really possible to get better quality from a lower bitrate?
If you are changing the compression algorithm of course it is possible. In H264, there are a lot of compression possibilities which are not used by the compression algorithm but which will be recognized by the decompression algorithm.
Any lossy compression works by throwing away bits of the picture that the viewer might not notice. You can lower the bitrate with better psychovisual and psychoacoustic models. You're still throwing away more information, but you're doing it in a way that the user is less likely to notice. This takes more CPU time on the compressor, a more optimised encoder, or a better algorithm.
I am TheRaven on Soylent News
It's not impossible to get better results out of lower bitrates, but you have to pay the penalty elsewhere, typically in encode/decode complexity.
If your decode hardware is fixed (it's generic HDTV hardware), then there is much less room for improvement, and half the bitrate is an enormous drop. It's no surprise that the BBC viewers complained.
I read the internet for the articles.
Nitpick: So 39% is "almost 50%"?? I would have called that "almost 40%". Then again that is a /. summary.
After logging in slashdot still does not take you back to the page you were on. It's been that way for 20 years.
They just remove the naughty bits.
Bitrate is only part of the equation -- the H.264 spec allows for a number of different ways to compress video, and it's up to the encoder to find out which is best for your video. Even in the same encoder, you can tweak dozens of settings in ways that dramatically change output quality -- usually a trade off between time and size.
x264 has beat every commercial encoder out there -- in some cases, on a level that would indeed render higher quality with half the bitrate.
Try watching a football game here in the US and you will see what crap quality can be. The turf turns into squares of blur when the camera moves, then returns to blades of grass when the picture is stationary. As soon as you spot it you will hate it. If you don't see it then OK for you.
I used to have a friend who could spot the two little circles in the top right of a movie in the theater telling the projectionist to change the reel. Once he saw them the movies were never the same again.
If you're watching a soap opera, you only need to see a few frames per week to follow the story. If you are watching a live sports event with a lot of action, most people will notice every dropped frame and compression artifact (I've noticed myself while watching the Olympics via satellite feed.) Methinks they did the testing on a relatively static video. Video compression works by (among other methods) creating a key frame, then sending diffs off that key frame for several frames. If every frame is completely different, compression does not work well.
I've abandoned my search for truth; now I'm just looking for some useful delusions.
For reference, the BBC HD content on iPlayer is 3.5Mb/s for 720p (no higher quality available). 9.7Mb/s is less than three times as much, so it probably won't be long before the streaming and broadcast signals are the same quality.
I am TheRaven on Soylent News
was the featureless black-screen video to 4'33" from John Cage. Results were far better at the lower bitrate. The absolute darkness was less blurry.
Nullius in verba
Lossy compression formats depend on an understanding of human perception. Nobody has a perfect model of the human brain, and nobody has a perfect algorithm for deciding what data to keep and what data to throw away.
If you have a better model of human perception than your competitors, then your encoder will yield higher quality output. If you spend 50% of your bits on things that nobody will notice, and I spend 25% of my bits on things that nobody will notice, then my 650kbps stream is going to look better than your 900kbps stream.
LAME did not win out as the MP3 encoder of choice just because it is free. It won out because its psychoacoustic model yields better-sounding MP3s at 128kbps than its competitors managed at 160kbps or even 192kbps.
I'll toss FIOS under the bus too. Verizon's HD varies greatly. I'm not sure if its the channel companies themselves or Verizon doing it...
Either way, I hate watching fast motion movies or tv shows where the bitrate is too low.
Try watching "How its Made" on discovery HD and watch how compressed things look as fast moving manufactured parts pass through machinery.
Same for HBO films etc.
Public: Shou£dn't you be ta£king in our £anguage?
Windows 3.1x calc: 3.11 - 3.10 = 0.00
But then iPlayer appears to use H.264, which allows for more efficient encoding than the MPEG-2 codec used for digital TV broadcasts.
Comment removed based on user account deletion
Now when we go to watch the Christmas special it will look like Cardboard sets, that wibble and wobble. The TARDIS will look utterly horrible and the Doctor will revert to a bloke from Liverpool with big eyes, big teeth, curly hair and a long scarf.
They also lowered the audio rate down to 16Kbps, so that rich orchestral music will sound like it came out of a cheap 1970's Moog.
Great, just when they updated the look of the show this will undo all of their work and it will look like the viewers were taken back to the 80's in an actual TARDIS.
Bravo BBC, Just Bravo......
Tsukasa: All I really want, is to be left alone...
Depending upon the configuration settings (frames per second, bit rate, I frame P frame structure etc.) it is most certainly possible to have a lower bit rate setting with better quality video than that of a higher bit rate setting. For example, if you drop the frame rate on a lower bitrate you often increase the quality of the video. So theoretically you can get easily the same quality at say 5 Mbps with a 15 fps as you can at 10 Mbps with 30 fps. I don't have specific numbers but subjectively (and empirically) it's quite possible.
There are definitely things that do make a difference here though, such as motion or high speed camera work. These types of video often suffer more noticeably than others so anyone watching sports, for example, will see the differences in quality more readily than someone watching a soap opera.
"Growing old is inevitable; growing up is optional."
They do expect everyone to get a new receiver. Freeview HD has just started it's rollout, although no receivers will be available until next month. It uses H.264 and DVB-T2.
A latent existence